Acoustic Transfer Assist (ATA) devices are used to help transfer toner to paper through the use of ultrasonic vibrations. ATA is especially valuable when transferring toner to rough, embossed, or otherwise uneven papers. A piezoelectric transducer is driven at its resonant frequency, with appropriate damping. The transducer is a very high Q resonant electrical circuit driven at its resonant frequency. The factor “Q” is a measure of the rate at which a vibrating system dissipates its energy into heat. A higher Q indicates a lower rate of heat dissipation. The vibration in the transducer is electrically analogous to current in the resonant circuit, and like any very high Q circuit, the current rises and decays relatively slowly in reaction to application or removal of a drive signal.
At certain points in the printing process, it is desirable for the transducer to cease the vibrations to avoid print quality defects. For example, if the transducer is vibrating in certain areas, toner can be undesirably transferred to mechanical elements of the printer and then transferred to other images, resulting in errors in those images. Typically, to turn the transducer off, a drive signal is simply cut off from the transducer. This method of turn off is relatively slow. The transducer continues to vibrate for approximately 5 ms after the drive signal is cut off. This type of decay is typical with any oscillating mechanical system. The existing delay between signal shut-off and transducer inactivity can produce defects in current ATA systems. Because of this delay, the space between sheets of media needs to be extended so toner is not accidentally applied to areas where it should not be, ultimately effecting how many sheets of print media can be processed in any given time period. The time it takes for the transducer to decay ultimately effects the operating speed of the printer. For high speed ATA enabled machines, this decay time can represent a significant delay in job processing times.